Henderson was forced to withdraw from Gareth Southgate's England squad at the European Championship with a hip injury, having been on the bench for the Three Lions' 1-0 triumph against Croatia on Sunday.
"While I'm delighted to be joining back up with England, my immediate thoughts are with Deano as I know how much it meant to him to be involved," Ramsdale posted to social media.
"I have now been given the honour and to be involved in a major tournament is what dreams are made of. This is a special moment for me and my family."
UEFA's Euro 2020 rules allow for teams to replace goalkeepers on medical grounds throughout the tournament.